In intensive care medicine, central venous catheters (CVCs) with several lumina, so-called multi-lumen CVCs, are frequently used. With these multi-lumen CVCs various parameters are ascertained, infusion solutions, blood and blood derivatives and pharmaceutical products are delivered via various lumina and blood samples taken for blood-gas analysis, haematological and biochemical tests. It is also known to introduce fibre-optic probes via a fibre-optic lumen in order for example to measure central venous oxygen saturation (Scv02).
A catheter with optical fibres is described in EP 1 402 917. The catheter system is suitable for the simultaneous, continuous, reciprocally uninfluenced measurement of central-venous oxygen saturation. It has a central venous catheter with a fibre-optic lumen and a fibre-optic probe which can be introduced into the fibre-optic lumen in order to take reflective oximetry measurements. To avoid a longitudinal displacement of the fibre-optic probe relative to the fibre-optic lumen a connector piece firmly connected to the fibre-optic probe and a counter-piece firmly connected to the catheter are provided which can be connected to one another.
Because of the fixedly prefabricated length of the fibre-optic probe and the firm connection of the fibre-optic probe to the connector piece, a precise matching of the individual fibre-optic probe to the central venous catheter to be used is necessary. In order to measure the central venous oxygen saturation via the probe, the tip of the probe projects beyond the distal end of the CVC by approximately 25 mm±5 mm It is thereby ensured that central venous blood flows round the probe and a measurement at this point gives the central venous oxygen saturation. Simultaneously, the tip of the probe must not lie in the right atrium, where it would lead to irritations of the heart.
Because of the different length of individual CVCs from different manufacturers it is therefore necessary to provide fibre-optic probes cut to different lengths for the very wide range of applications, which are matched to the respective CVC in terms of the length such that these criteria are met. If a fibre-optic probe which is too short is used by mistake, the correct value of the central venous oxygen saturation cannot be ascertained, as the tip of the probe is then still in the CVC. If a fibre-optic probe which is too long is chosen, there is a risk that the probe will come to rest in the right atrium, leading to irritations of the heart or the death of the patient. A probe which projects too far from the CVC is possibly not adequately guided and can then easily be unfavourably positioned, e.g. rest against the vascular wall or bend.